This invention relates in general to tapered roller bearings, and more particularly to tapered roller bearings in which true rolling contact exists at all critical surfaces during operation of the bearing.
Antifriction bearings come in several basic configurations, but irrespective of its configuration, an antifriction bearing includes a pair of ring-like races and rolling elements arranged in at least one row between the races. The rolling elements contact raceways on the races, and when the bearing is set in operation, the rolling elements roll along those raceways and around the axis of the bearing.
When the rolling elements take the form of cylindrical rollers, the bearing has the capacity to take heavy radial loads, but is not very satisfactory for transmitting thrust loads. Moreover, cylindrical roller bearings usually have radial clearances, and thus are not suitable in applications requiring stability, rigidity and a good measure of precision. A ball bearing in which the rolling elements are balls may have its raceways oblique to the axis of the bearing so that the bearing takes radial and thrust loads. When arranged in pairs, angular ball bearings may be adjusted against each other to eliminate end play--and radial clearances as well--but the load capacity of an angular ball bearing is relatively low. A tapered roller bearing possesses the advantages of both cylindrical roller bearings and angular ball bearings. It has the capacity to carry heavy radial loads and also thrust loads, all through its tapered rollers and the raceways along which they roll. As a consequence, a tapered roller bearing may be adjusted to eliminate clearances between its rollers and raceways.
Owing to the tapered geometry of a tapered roller bearing, the tapered rollers tend to move up the raceways and unless restrained will be expelled from the bearing. For this reason, the conventional tapered roller bearing has a thrust rib at the large end of one of its raceways, usually on the inner race which is called the cone. As the rollers roll along the raceways, the large end faces of the rollers bear against the thrust rib and the rollers remain in place axially. While generally pure rolling contact exists between the tapered side faces of the rollers and the raceways, the end faces of the rollers slide and spin along the face of the thrust rib. In the absence of adequate lubrication, the bearing may fail at this critical area, for here the friction is highest within the bearing. Moreover, due to the slide and spin motion between the roller ends and the thrust rib, the torque within a tapered roller bearing operating at low speed, is relatively high and, to a measure wear as well.